The invention pertains to a method and to an apparatus for controlling the brake system of a vehicle according to the introductory clauses of the independent claims.
A method and an apparatus for controlling the brake system of a motor vehicle are known from WO-A 94/13517, in which, to ensure the optimum distribution of the braking force between the front and rear axles, the difference between the wheel rpm's of the front axle and the wheel rpm's of the rear axle is determined. This slip between the front and the rear axle is compared with a predetermined limit, the absolute value of which is larger when the vehicle is driving straight ahead than when it is driving around a curve. When the detected slip exceeds this defined limit, any further pressure increase in the rear-axle brakes is prevented. Even though two different threshold values are specified to deal with two different actual driving situations, it is still possible for the pressure level at the rear axle to be too high. This is especially the case when the vehicle is traveling straight ahead, the driver brakes, the brake system stabilizes at close to the ideal braking force distribution, and the vehicle then enters a curve. Because the pressure level in this case is too high, the rear wheels tend to lock, which is reduced by an antilock protective function. When the antilock protective function is activated, pressure is reduced in the rear-wheel brakes; because of the associated startup of the return pump at this point, a strong reaction is produced at the brake pedal. This sudden reaction at the brake pedal can confuse the driver and thus lead to unwanted situations.
It is therefore the task of the present invention to provide measures for ensuring the almost complete stability of the vehicle in the partial braking range even without any intervention by the antilock protection. At the same time, the driver should experience little or no reaction at the pedal.